CA2023004C

CA2023004C - Removal of trialkyl arsines from fluids

Info

Publication number: CA2023004C
Application number: CA002023004A
Authority: CA
Inventors: Gerhard P. Nowack; Patricia A. Tooley; Joseph B. Cross; Marvin M. Johnson; Ted H. Cymbaluk
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1989-11-21
Filing date: 1990-08-09
Publication date: 1999-03-30
Anticipated expiration: 2010-08-09
Also published as: NO178531B; EP0429053B1; US4992620A; JPH03181309A; CA2023004A1; DE69016360T2; DE69016360D1; JP2660093B2; EP0429053A1; NO905051L; NO905051D0; NO178531C

Abstract

Trialkyl arsines are removed from fluids, in particular gases, by contacting with a solid sorbent material containing at least one manganese oxide (preferably MnO2) and at least one Group IB metal oxide (preferably CuO). In a preferred feature, the used solid sorbent material is regenerated by oxidizing treatment, washing with an aqueous liquid, and drying.

Description

2 ~ 32 7 3 7CA

REMOVAL O~ TRIALK~L ARSINES FRON FLUIDS
Background of the Invention This invention relates to the removal of trialkyl arsines -from Eluids by means of solid sorbents. In another aspect, -this invention relates to the removal of trialky] arsines from gases, in particular hydrocarbon-containing gases.
Materials for adsorbing and/or absorbing unsubstituted arsine (AsH3) are well known. However, many of these materials are ineffec-tive for the sorption of trialkyl arsines, which may be present as undesirable impurities in natural gas streams produced at some well sites. This invention provides sorbent materials which are ~uite effec*ive in removing trialkyl arslnes from fluids, in particular gases, by sorption (i.e., adsorption and/or absorption).
Summary of the Invention It is an object of this invention to provide a process for removing trialkyl arsines from fluids. It ts another object of this invention to provide a process for removing trialkyl arsines from gases, in particular hydrocarbon-con-taining gases. Other objects will become apparent from the detailed description of the invention and the appended claims.
In accordance wi-th this invention, a process for at least partially removing trialkyl arsines from a fluid (preferably a gas) comprises the step of contacting a flllid feed which contains at least one trialkyl arsine with a solid sorbent material comprising (preferably consisting essentially of) (a) at least one manganese oxide and (b) at least one oxide of at least one metal of Group IB of the Periodic Table 2 ~ 3~l (as definecl on page 852 of Webster New Collegiate Dictionary, 1977);
wherein said contacting :Ls carried out at such contacting condi-tions as to obtain a fluid product having a lower trialkyl arsine content than said feed, and -to obtain a used sorbent material containing that portion of said at least one trialkyl arsine which has been removed from the feed. Preferably, the sorbent material is a Hopcalite comprising MnO2 and CuO.
Detailed Description of the Invention The term "trialkyl arsine", as used herein, refers to compounds having the general chemical formula of R3As, wherein each R is a radical independently selected from among alkyl groups (straight and/or branched), having 1-6 (more preferably 1-3) carbon atoms per molecule. Particularly preferred trialkyl arsines are trimethyl arsine, triethy] arsine and dimethyl ethyl arsine and diethyl methyl arsine.
Any suitable liquid or gaseous fluid stream which contains trialkyl arsine(s) can be used as feed in the process of this invention.
Preferably, the feed is gaseous. Non-limiting examples of suitable gaseous feeds are: natural gas; gaseous petroleum fractions comprising paraffins and oleflns containing 1-6 carbon atoms per molecule; and gaseous products obtained by thermal and catalytic cracking of petroleum, shale oil or coal. Generally, these gases comprise methane, ethane, ethylene, propane, propylene, n-butane, isobutane, butenes; and the like. These gas streams can (but do not always) contain o-ther impurities, such as hydrogen sulflde, carbonyl sulfide ~COS), mercaptans, organic sulfides, carbon monoxide, carbon dioxide, inert gases (N2, He, Ne, Ar), and the like. Other arsenic compounds may also be prssent in the fluid stream which is treated by the process of this invention, such as AsH3, RAsH2, R2AsH, R3AsO (trialkyl arsine oxides), R3AsS (-trialkyl arsine sulfides), and the like; wherein R is an alkyl group, as defined above. It is also possible to have trlphenyl arsine, dialkyl phenyl arsines, dialkyl cycloalkyl arsines, and the like present in the feed. PreEerably, free oxygen is substantially absent from -the feed.
~ enerally, the total concentration of the trialkyl arsine~s) in the feed (preferably gaseous) is in the range of from about 1 ppb (1 ~ 32737C~

part by weight of trifllkyl arsine per billion parts by wsight of feed) to about 0.1 weight-%, preferably abou-t 0.5-100 ppm (parts by weight trialkyl arsine per million par-ts by weigh-t of fsed). The concentrations of the other impurities and the exact compos:i-tion of -the fsed will widely vary from feedstock to feedstock.
Ths sorbent materials which are used in -the process of this invention compriss at least one manganese oxide, preferably MnO2, and a-t lcast one oxide of a Group IB metal (i.e., Cu and/or Ag and/or Au);
preferably copper. Any suitable manganese oxide content in the sorbent ma-terial can bs used, preferably about 30-90 weight-~ MnO2, more preferably about 40-80 weight-% MnO2. Any suitable Group IB oxide con-ten-t in the sorben-t material can be used, preEerably about 3 to abou-t weight-%, mors pre~erably about 10-45 weight-% metal oxide (preferably CuO).
Pref~rred sorbent materials are Hopca]ites, which are ccmmercially available as carbon monoxide oxidan-ts and sorbents (e.g., for gas masks). Thers are two main formula-tions of ~lopcalite:
Hopcalite I is a mixture of about 50% MnO2, about 30% CuO, about l5%
Co203, and about 5% Ag20; Hopcalite II contains about 60% MnO2 and about 40% CuO (David R. Merrill and Charles C. Scalione, J. Am. Chem.
Soc., 43, 1921, p. 19~2). A Hopcalite II material can also bs prepared in a laboratory by dissolving salts of Mn and Cu in water, passing an oxidizing gas (e.g., air) through the solutlon, adding an alkaline material te.g., dissolved NaOH) to the oxidized solution so as to coprscipitate oxides/hydroxides of Cu and Mn, separating ths coprecipitate from the solution, washing the coprecipitate, drying it, and heating it (preferably at about 150-250~C for about 10 minutes to about 10 hours).
The sorbent particles can have any suitable surface area (such as about 10-500 m2/g, as measured by the B.E.T. method employing N2), any suitable shape ~spherical, cylindrical, ring-shaped, trilobal etc.) and any suitable size (such as about 1-20 mm diameter for spherical particles).
Any suitabls contacting conditions can be employed in the sorption process of this invsntion. G~nerally the tempsrature in the 4 ~ 3 contacting zone is in the range of from about -~0 to about 100~C, preEerably about 20 to abou-t 50~C. Generally the pressure in the contacting zone is in -the range of from about 1 to about 500 atm., preferably about 1 to abou-t ~0 atm. Generally the gas hourly space velocity of the gaseous feed in the contacting zone is in the range of from about 1 to about lO,OOn volume of feed/volume oE sorbent/hour, preferably about 1,000 to about 3,000 volume/volume/hour, measured a-t about 25~C/l a-tm. Generally the contacting is continued until trialkyl arsine breakthrough occurs i.e., when -the treated product contains more trialkyl arsines than can be tolerated, such as about 50 ppb.
Treatment of the feed streams, in accordance with the process of this invention, can be carried out in any suitable manner. For exampls, in a preferred embodiment a bed of -the sorbent is placed as a fixed bed in a confined zone, and a fluid stream (preferably a gas) is passed therethrough in either upward or downward flow. Other suitable, yst less preferred methods of treatment can include a fluidized operation in which the feed and the sorbent particles are maintained in a state of turbulence under hindered settling condltions in a confined zone, moving bed operations in which the sorbent passes as a moving bed concurrently to or concurrently with the feed, etc. In a fixed bed operation of a continuous process, the flow of fluid can be rotated between two or more sorbent beds with at least one being in regular operation, the other being in a regeneration mode. Continuous processes are preferred~ but it is understood tha-t batch -type operations can be employed when desired.
The used sorbent composition (in partic~lar Hopcalite) after it has reached its maximum capacity for trialkyl arsines is capable of being regenerated. Regeneration can be accomplished by a multi-step process comprising an oxidation step employing an oxidizing agent, preferably a free oxygen containing gas (e.g., air), generally at ambient conditions (about 25~ C/l a-tm.) for a time sufficlent (preferably for abou-t 10 minutes to about 10 hours) to at least partially oxidi~e the absorbed arsine(s), e.g., to arsine oxide(s) (i.e., R3AsO), passing an aqueous liquid, preferably ~ater or an aqueous solution containing hydrogen peroxide (or any other suitabLe oxidizing 3z737CA

agent), -through Lhe oxidlzed bed of sorbent material so as to dissolve any arsenic compound(s), e.g., R3~sO, and thereaf-ter drying the washed sorbent material (preferably at about 50-120~C for about 10 minutes -to about 10 hours) so as to obtain a regenerated sorbent material (containing less As than the unregenerated used sorbent material) which can be reused in the process of this invention. The above-described regeneration procedure can be repeated (once or more than once).
It is wi-thin the scope of this invention -to employ a combination of sorbents, such as a first bed of PbO/Al203 or a CuO/ZnO-containing material (described in U.S. Patent ~,5~3,1(~8) for removal of a ma~jor portion of AsH3 or H2S or bo-th, and a-t leas-t one subsequen-t downstream bed containing at least one of the sorben~
materials of this invention for absorbing primarily trialkyl arsines.
This multi-bed operation can be carried out in one reactor containing a layer of PbO/Al203 or CuO/ZnO material (or any other known sorbent for AsH3 and H2S) and a downs-tream layer of a trialkyl arsine sorben-t of this invention. Or the multi-bed operation can be carried ou-t using two or more separats sorption reactors: at least one first reactor containing PbO/Al203 or a CuO/ZnO material (or any other known sorbent for AsH3 and H2S) and at least one second reactor containing the trialkyl arsine sorbent of this invention, wheroin the feed passes -through the first reactor(s) and thereafter through the second reactor(s).
The process of this invention will bs further illustrated by the following non-limiting example.

Example This example illustrates the absorp-tion of an alkyl arsine by several copper-containing sorbent materials.
A nitrogen gas stream was passed through a flask containing liquid-trimethyl arsine (provided by Strsm Chemicals, Inc.), which was cooled to about -78~C by placing -the flask in a dry ice/acetone mixture.
The exiting gas stream, which consisted essentially of N~ and trimethyl arsine (with no H2S present), was passed through a glass tube of about 7 mm diameter and about 15 cm ]ength containing abou-t l gram o-E one of the 32737C~

3 ~

sorbents to be tested. The gas which exi-ted the absorptlon tube was passed through an aqueous solution of KMnO4 and then to a flow meter.
The flow rate of the feed gas was about 1800 cc per hour at about 25~C.
When trimethyl arsine breakthrough occurred (i e., when the sorbent had reached its maximum arsine absorption capacity), the purple color of the KMnO4 solu-tion turned brownish. After arsine breakthrough had been detected, -the flow of the trimethyl arsine containing gas stream was stopped, and a purge stream of pure nitrogen was passed through the sorbent ma-terial for about 1-2 hours so as to purge unabsorbed trimethyl arsine therefrom. The absorption tube containing the sorbent and absorbed trimethyl arsine was weighed. The difference between this weight and the initial weight of -the tube wi-th fresh sorbent was -the weight of absorbed trimethyl arsine.
The following sorbent ma-terials were tested: (1) a commercial Hopcalite having the approximate chemical formula of CuO-MnO2 (provided by Callery Chemical Company, Pittsburgh, PA); comprising about 50 weight-% Mn, about 12 weight-% Cu and 0.3 weight-% Nfl); (2) CuO/ZnO
(substantially as described in Example I of U.S. Patent 4,S~3,148;
pxovided by BASF Wyandotte Corporation, Parsippany, NJ, under the product designation "R3-12"); (3) Cu(II) chromite (CuO/Cr203;
substantially as described in U.S. Pa-tent 4,605,~12; prov.ided by United Catalys-ts, Inc., Louisville, KY, under the product designation l'G-22").
Test results are summarized in Table I.

Table I
Millimoles Trimethyl Arsin~e Sorbent Absorbed Per Gram Sorbent Hopcalite 0.60 CuO/ZnO o Copper(II) Chromite O

) at -trialkyl arsine breakthrough Tes-t results in Table I show that Hopcalite, unexpectedly, absorbed trimethyl arsine while two other Cu oxide-containing materials (which are known AsH3 sorbents) were not effective as trimethyl ars.ine sorben-ts.

3Z737(~
7 ~ ;

Example II
This exflmple lllustrates the regenera-tion of used Hopcalite which contained absorbed -trimethyl arsine.
A stream of air (at room temperature) was passed for one hour over a sample of spent llopcalite which contained about 4-5 weight-%
trimethyl arslne. The thus-treated Hopcalite material was washed twice with distillated water (so as to dissolve oxidized trimethyl arsine), and was then dried a-t 150~C for 12-14 hours. The dried regenerated Hopcali-te was tested for trime-thyl arsine sorption, subs-tantially in accordance with the procedure described in Example I. At trimethyl arsine breakthrough, 0.047 g trimethyl arsine had been absorbed by 1.57 g regenerated Hopcalite. Thus 3 the maximum absorption capaci-ty of -the water-washed and dried regenerated Hopcali-te was 0.25 millimoles -trimethyl arsine per gram regenerated sorbent.
In a separate test, a sample of ano-ther spen-t Hopcalite which contained about 7 weight-% As (as trimethyl arsine) was treated with flowing air at room temperature for one hour, washed three times with about 30 weight-% of an aqueous H2O2 solution, and dried at 100~C for about 16 hours. The thus-treated Hopcalite was tested for trimethyl arsine sorption, substantially in accordance wi-th the procedure described in ~xample I. The maximum absorption capacity of this oxidized, H202-treated and dried Hopcalite was 0.61 millimoles trimethyl arsine per gram sorbent. When pure water was substituted for the aqueous H202 solution in the above-described regeneration procedure (employing spent Hopcalite containing about 7 weight-% As), the absorption capacity of the regenera-ted Hopcalite was only 0.46 millimoles trimethyl arsine per gram regenerated sorbent. Thus, washing with aqueous H202 (after air oxidation) is a preferred mode for regenerating spe~lt, trialkyl arsine containing Hopcalite.
Reasonable variations and modifications, which will be apparent to those skilled in the ar-t, can be made within the scope of the disclosure and the appended claims without departing from the scope of this inv~ntion.

Claims

1. A process for removing trialkyl arsines from gases comprising the step of contacting a gaseous feed which contains at least one trialkyl arsine with a solid sorbent material comprising a hopcalite; wherein said contacting is carried out at such contacting conditions as to obtain a fluid product having a lower trialkyl arsine content than said feed.

2. A process in accordance with claim 1, wherein said feed is a hydrocarbon-containing gas.

3. A process in accordance with claim 1, wherein said trialkyl arsine has the chemical formula of R3As with each R being independently selected from the group consisting of alkyl groups containing 1-6 carbon atoms.

4. A process in accordance with claim 3, wherein aid alkyl groups contain 1-3 carbon atoms.

5. A process in accordance with claim 1, wherein said at least one trialkyl arsine is selected from the group consisting of trimethyl arsine, triethyl arsine, dimethyl ethyl arsine and diethyl methyl arsine.

6. A process in accordance with claim 1, wherein said feed contains about 1 ppb by weight of about 0.1 weight percent of said at least one trialkyl arsine.

7. A process in accordance with claim 1, wherein said solid sorbent material contains about 50-60 percent by weight MnO2 and about 30-40 percent by weight CuO.

8. A process in accordance with claim 1, wherein said contacting conditions comprise a temperature in the range of from about -20° to 100°C.

9. A process in accordance with claim 1, wherein aid feed additionally contains H2S.

10. A process for at least partially removing trialkyl arsines from gases comprising the steps of:

(1) contacting a gaseous feed which contains at least one trialkyl arsine with a solid sorbent material comprising a hopcalite; under such contacting conditions as to obtain a fluid product having a lower trialkyl arsine content than said feed and to obtain a used solid sorbent material containing that portion of said at least one trialkyl arsine which has been removed from said feed.
(2) treating said used solid sorbent material with an oxidizing agent for a time sufficient to at least partially oxidize the absorbed trialkyl arsine(s);
(3) passing an aqueous liquid through said solid sorbent material having been contacted with said oxidizing agent, so as to obtain an aqueous solution of at least one arsenic compound and a wet regenerated solid sorbent material containing less arsenic than said used solid sorbent material; and (4) drying said wet regenerated solid sorbent material.

11. A process in accordance with claim 10, wherein said feed is a hydrocarbon-containing gas.

12. A process in accordance with claim 10, wherein said trialkyl arsine has the chemical formula of R3As with each ?R being independently selected from the group consisting of alkyl groups containing 1-6 carbons atoms per molecule.

13. A process in accordance with claim 12, wherein said at least one trialkyl arsine is selected from the group consisting of trimethyl arsine, triethyl arsine, dimethyl ethyl arsine and diethyl methyl arsine.

14. A process n accordance with claim 10, wherein said oxidizing agent is a free oxygen containing gas.

15. A process in accordance with claim 10, wherein said aqueous liquid is water.

16. A process in accordance with claim 10, wherein said aqueous liquid is an aqueous solution of hydrogen peroxide.

17. A process in accordance with claim 10, wherein the dried regenerated solid sorbent material obtained in step (4) is re-used in step (1).

18. A process in accordance with claim 16, wherein said solid sorbent material contains about 50-60 percent by weight MnO2 and about 30-40 percent by weight CuO.

19. A process in accordance with claim 10, wherein said feed is a gas and said contacting conditions comprise a temperature in the range of from about -20°
to 100°C.

20. A process in accordance with claim 10, wherein said feed additionally contains H2S.